Question

Difficulty: Very hardDesign Traffic Routing and Failover Strategies

An enterprise is designing a global disaster recovery and traffic routing solution for a hybrid workload deployed across the East US and West US regions. The workload consists of two primary services:

1. A web application API running on HTTPS that requires Web Application Firewall (WAF) protection, URL path-based routing (routing `/static/*` to storage and `/api/*` to compute), and SSL/TLS termination at the edge.
2. A latency-sensitive database replication daemon communicating over custom TCP port 14331433. The database clients have a legacy configuration that hardcodes or aggressively caches DNS query results, ignoring any DNS Time to Live (TTL) values.

Which two routing and load balancing strategies should you implement to satisfy the requirements for both services?

  1. Deploy Azure Front Door for the HTTPS web API to handle SSL/TLS termination, path-based routing, and WAF protection at the global edge.Answer
  2. Deploy an Azure Cross-Region Load Balancer (Global Tier) to expose a single static Anycast IP address for routing the custom TCP port 14331433 traffic.Answer
  3. C
    Deploy Azure Traffic Manager for the HTTPS web API to route client requests using the performance routing method and offload SSL/TLS decryption.
  4. D
    Deploy Azure Traffic Manager for the TCP database replication daemon to perform DNS-based failover with a 1010-second DNS TTL.
  5. E
    Configure the database tier to replicate write operations using Read-Access Geo-Redundant Storage (RA-GRS) to allow simultaneous database writes in both East US and West US.

Answer

Deploy Azure Front Door for the HTTPS web API to handle SSL/TLS termination, path-based routing, and WAF protection at the global edge, and deploy an Azure Cross-Region Load Balancer (Global Tier) to expose a single static Anycast IP address for routing the custom TCP port 14331433 traffic.
The correct architecture combines Azure Front Door and Azure Cross-Region Load Balancer. Azure Front Door handles the HTTPS web API because it is a global Layer 77 service that natively supports TLS termination, path-based routing, and WAF integration. The Azure Cross-Region Load Balancer handles the custom TCP port 14331433 database replication traffic because it operates at Layer 44 and uses Anycast to expose a single static IP address. This static IP ensures that even if clients aggressively cache DNS records and ignore TTL, traffic is automatically rerouted at the network layer to the healthy region during a failover, bypassing the DNS propagation delay entirely.

Step-by-Step Solution

1
Analyze the global routing and feature requirements for the HTTPS web application API.
Identified the need for Layer 77 traffic management including SSL/TLS termination, URL path-based routing, and WAF protection at the edge.
These capabilities require an application-aware global routing service rather than a simple DNS-based or Layer 44 router.
2
Evaluate the network and client constraints for the database replication daemon on port 14331433.
Identified that the daemon runs over a custom TCP port and clients aggressively cache DNS records, ignoring TTL.
This rules out DNS-based load balancing (Azure Traffic Manager) due to failover failure risks, and rules out Azure Front Door because it does not support arbitrary non-HTTP TCP ports.
3
Map the evaluated requirements to optimal Azure global load balancing services.
Select Azure Front Door for the HTTPS Web API and Azure Cross-Region Load Balancer (Global Tier) for the TCP replication daemon.
Azure Front Door delivers Layer 77 global routing and WAF, while Cross-Region Load Balancer uses Anycast-based routing with a static IP to support Layer 44 TCP traffic without relying on DNS updates for failover.

Key Concept

Designing multi-region traffic routing strategies using Anycast IP (Cross-Region Load Balancer) versus Application-layer routing (Azure Front Door) based on protocol (TCP vs HTTPS) and client DNS behavior.
Estimated Time:3m 0s
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